Ten Hag substituted Ronaldo during Sunday's 0-0 draw with Newcastle.
Saha told Boyle Sports: "He was disrespected. I don't totally agree with Ten Hag's management. I understand why Ronaldo was upset in the game against Newcastle, because he believes he can score. Lately he hasn't been very lucky or very effective, it happens. You have to understand that he is not a robot.
"When people are tired, Ronaldo is a killer, there's no one better than him to score important goals under pressure. He did it last year and there's no reason why he can't keep doing it this season.
"There's no physical indication that he is slowing down."